Any individual who spends the vast majority of their time declaring that the other party in a conversation is ignorant, or doesn't understand anything, or doesn't have knowledge about the subject matter, or does not make sense,... that individual wastes a proportionate amount of time that they could have spent showing others how much they do understand.

But it's not a bug. It's just what happens when you take a premultiplied image into a non-premultiplied world and have to deal with colors under the transparency values of zero.

Ya know, for a second there I almost missed the relevance of this comment. You're saying now that this is a circumstance of bringing a premultiplied image into non-premultiplied workspace? I thought for second,.... maybe. Then thinking about all the tests I've run on this in the past, the fact EXR images didn't generate these mangled images on output while PIC and IFF do for example....

I thought no....this doesn't seem right.

Thinking back I realized I had tested non-premult images into photoshop but never out of photoshop. So I had to be sure and I ran another expriment.

I created a new XSI scene this time with a white ball instead of a red one.

I render it out as PIC with "Premultiply with Alpha" turned off in Softimage.

This is what I get

If you zoom into the edge of this image you will see the telltale signs of it being non-premultiplied.

But it's not a bug. It's just what happens when you take a premultiplied image into a non-premultiplied world and have to deal with colors under the transparency values of zero.

And then what you said back in post #203

You said

Chris Cox wrote:

Photoshop may change some color values on some file formats when opening -- because the color values have no meaning in 100% transparent areas. Again, Photoshop is straight color, not premultiplied color -- this is an important concept. If Photoshop were limited to premultiplied color, it could not do most of the editing it does (or the editing would be much, much slower and more prone to adding artifacts).

Here you said that the some color values are changed by Photoshop on open because they have no meaning in 100% trasnparency.

One can only deduce that any color, typically black located 1:1 with 100% trasnparency is changed, on purpose.

And one can further deduce that since you say it has no meaning, therfore you think it is unneccessary and eligible to be discared.

But if the image is non-premultiplied to begin with, why would it need to be changed at all? Which the above illustration shows that it is being changed regardless what it really is, premult or non premult.

It further made me wonder if it is so absolutely required and important that the color corresponding to 100% transparency be changed to white or null, then why isn't this being changed

Why don't these regions have to be white? Won't they interfere with the non-premultiplied space?

But what color are they really? I can't interrogate this jpg, its compressed and will lie to us. I can't interrogate the image further in Photoshop it will only compound the problem. So I bring it into Softimage FXTree

Its black 0, 0, 0 just like in the original image.

So why doesn't this black need to be removed?

WHy isn't it important to change this color when it is with everything else is?

But what was changed, the white around the ball, surrounds a near perfect square geometry. Not jagged areas, but the square bounding perimeter of the ball.

What impact does this exterior white area have? Especially since it is rarely adjacent the edge perimeter which is what is most reliant on being non-premultiplied?

That little pixel, its Black0,0,0

Only two white pxels on this side even touch the edge of the ball. Since it is non premult, the exterior pixels will likely end up near 0% percent opacity anyay.

So why is it necessary, as you claim, to get rid of some of the external 100% transparent RGB pixels? But not all?

In other words, the logic is like this. If the pixels adjacent to the ball's edge can be Black0,0,0, and they would matter most in optimizing the non-premult comp, and they were originally Black0,0,0 anyway, why do the pixels farthest from the ball have to be changed and not those closet the ball?

Sorry to borrow the phrase, but that doesn't make any sense.

But then I recalled that you said

Chris Cox wrote:

If Photoshop were limited to premultiplied color, it could not do most of the editing it does (or the editing would be much, much slower and more prone to adding artifacts).

Which is why I assumed that the pixels that are now white were actually turned into null pixels, but written as white on the save(IE Assumed background color is typically always white in Photoshop. Transparency is "assumed white" on print) because Photoshop can't put the colors back anymore. If it discarded the pixels to optimize the file there would be no reference to what they really are anymore, because if they had been saved, they wouldn't be discarded. Then it would be really easy to put them back. That was the guess anyway.

So what is really going on here?

The image opened in Photoshop was not premultiplied.

There are some colors under 100% transparency that are preserved and some under 100% transparency that were thrown away.

You said some colors are being changed if they have no meaning in 100% trasnparency

and my image still looks like this

So, are pixels being thrown away in this image?

Which ones if they are?

Why aren't all colors corresponding 100% tranparency changed?

And why did the saved non-premult image produce the same result as the saved pre-mult image?

Joey

Oh yes, and does "100% transparent" also mean the same pixels as you define by saying "transparency values of zero". You described 100% transparency as being the color pixels that were thrown away(that could only mean the pixels not comprising the ball) but you also descibe colors UNDER transparency values of 0. Colors under would insunuate that the colors are hidden, since colors over would be assumed visible. Though transparency value of zero could also imply 0% transparency or opaque. Can you please clarify this? Or is "transparency value of zero" another way of saying 0,0,0?

Toast - as already explained ad nauseum: as much as possible is ALREADY being kept intact.

You simply aren't seeing things the way you are used to (WYSIWYG versus "imagine if").

Or some people don't even understand what they're seeing.

TGA is a special case - the file format says we should load the fourth channel as transparency. But when we did that too many people complained. We went backto loading it as an alpha channel instead. That means that TGA is useless for compositing, but sometimes gives you what you want, unless you expected it to be premultiplied, etc.

We might be able to add options, but we don't want to bother everyone using file formats as they were intended with options that they don't need or care about. So we have to be careful -- that's what we ALREADY discussed in this topic.

Apparently some do need instruction, becuase they can't get basic concepts straight enough to discuss them in any rational manner.

Toast - as already explained ad nauseum: as much as possible is ALREADY being kept intact.

Except premultiplication, which isn't even supported much less kept intact.

Oh and IFF and PIC file RGB channels are ALREADY far from being kept intact(see above). Their alphas look great though.

You simply aren't seeing things the way you are used to

Which means we've been seeing alphas separated from the image longer than Photoshop has been around. And we will continue to do so indefinetely, regardless how you want us to see them.

WYSIWYG versus "imagine if"

The day that a transparency layer, derived from alpha and displayed over checkerboard, is WYSIWYG, is the day that alpha channel is the same as alpha/transparency/opacity/mask.

You defined that level of rigidity to specification. Not I.

TGA is a special case

Its the primary case. Its how we have used, displayed, and manipulated these images and alphas in this industry for almost 3 decades. No effort by you or Adobe will ever change that,

Resistance is futile.

the file format says we should load the fourth channel as transparency. But when we did that too many people complained

Because they were right about how they used their images and you are wrong about how they used their images.

We went backto loading it as an alpha channel instead. That means that TGA is useless for compositing,

Thats just not true....

Load selection>Channl:Alpha 1

Select>Inverse

Layer>Add Layer Mask>Reveal Selection

Now you have a composite via layer mask. Which is what we want from images rendered with alpha.

We don't want automated transparency layers from alpha.

but sometimes gives you what you want, unless you expected it to be premultiplied, etc

We can't use premultiplied images with Transparency or Layer Mask. We have to render our images specifically as not premultiplied just to use them with Photoshop anyway. So what difference does "expecting it to be premultiplied" make.

We might be able to add options, but we don't want to bother everyone using file formats as they were intended with options that they don't need or care about.

Stop obsessing about what you think you can't do or what you think you have to do. Start thinking outside of the Photoshop. Just a little.

Add the options, then put a preference in the software to switch between Standard Image Loading and Advanced Image Loading. Advanced would turn the option dialogs on, standard ignores the dialog. Set Standard as the default install setting. Then all those folks that don't want to be bothered with our workflow don't have to deal with. In the meantime we are smart enough to find the preference and flip the switch. We'll be more than happy to search all bugger day long to find the switch.

So we have to be careful -- that's what we ALREADY discussed in this topic.

As carfeul as you are with the IFF and PIC files?

Apparently some do need instruction, becuase they can't get basic concepts straight enough to discuss them in any rational manner.

Thats correct, the basic concept is that we create our alpha channels and we want full control over our alpha channels. Thats as rational as it gets.

Well.. I was searching for a solution regarding EXR and alpha and found this thread. Man.. I swear, this is THE best thread in the entire Web. I dont remember when I was laughing that much. Chris, you are my favorite

The thread is now over 1 year old, and we still did not get the solution to the simplest case one can imagine. What can be simpler? Make alpha as separate channel as it was in previous version? Wow.. I need a rest from laugh

Back in the days of Photoshop 7. When it was released, there was a change in the way TGA files are loaded. There was exactly same situation as now with EXR - alpha now applies to the whole image and turns pixels into transparent, instead of loading as fourth channel. At that time, the problem WAS fixed by ADOBE. They released another loader, that user could install. Here is the link with description of problem:

Here is a quote from official Adobe statement (yes, its the place where you are working!):

Versions of Adobe Photoshop earlier than version 7.0 saved the first alpha channel in a file into the fourth channel when writing Targa files. Photoshop 7.0 changed the application's default behavior to save transparency information instead of an alpha channel, resulting in incompatibility with some existing workflows. In response to user feedback, this plug-in restores the earlier behavior of the Targa plug-in.

You see, they DID admit that problem exists and DID release an alternative loader. So what you can say now? Its still impossible?

Wow. I just read this entire ridiculous thread and I gotta say it is just about the most pointless waste of time I have ever experienced. I have been stymied for years as to why Photoshop suddenly forgot how to open a tiff file with a matte in it. It really has been a bottleneck and a puzzling quirk in an otherwise remarkable professional tool.

Chris, dude. Sorry to be blunt here but you're just about the most pig-headed person I've ever come across. But I say this in the nicest way. Okay, you win. You win, man! You're the smartest person on earth. You're right about everything. We're all ignorant morons and you're the main man who's righter than right.

Now can we please just have a ******** OPTION, for crying out loud, to open a file with a matte in it exactly as it was saved. Simple solution. Nobody cares if it's the right way or the wrong way. We just want to open the file without automatically applying the transparency information to the image. Is great big Adobe too stupid to figure that out or what?

Sorry to be blunt here but holy cow. I really don't know how else to put this except maybe in the future you could save us all about three hours of reading by just saying something like "Gee, thanks for the suggestion, we'll look into it."